1. Field of the Invention
The present invention relates to an exposure device (exposure apparatus) provided with a plurality of light-emitting sections (a plurality of blinking sections or intermittent light-emitting sections such as LED heads, etc.), and a method for producing the exposure device.
2. Description of the Related Art
An exposure member (for example, LED head (Light Emitting Diode head), etc.) which has a plurality of light-emitting sections arranged in a row and which expose a photosensitive or photoconductive body is conventionally used in an image-forming apparatus. Such an exposure device is provided with a light-emitting element such as LED, etc. and a casing which holds the light-emitting element. The exposure device needs to be subjected to positioning (subjected to positional adjustment) correctly with respect to the photosensitive body so that the exposure position with respect to the photosensitive body is accurate so as to form a satisfactory image. An exposure device in which a frame supporting a photoconductive drum (photoconductive body) is positioned with respect to an LED head (exposure member) by using a structure having a concave-convex shape, etc.
The exposure device which exposes the photoconductive drum is provided with an LED head having an LED, an lens array which forms an image (images) of a light emitted from the LED on the photoconductive drum as an erecting image, at ×1 magnification; and a housing which supports the LED and the lens array. The lens array includes GRIN lenses which are made of glass, which are gradient index lenses (each having refractive index gradient) and which are aligned in a row or in a plurality of rows; and the lens array is formed in an elongated shape extending in the axis direction of the photoconductive drum.
Further, the elongated lens array is arranged in the housing so as to protrude downward form the lower surface of the housing, and the lens array has the corner portions, on both ends in the longitudinal direction of the lens array, which are pointed substantially at a right angle.
Furthermore, in the above-mentioned exposure device, a spacer for maintaining the spacing distance, in the optical axis direction, between the LED head and the photoconductive drum is arranged between the LED head and the photoconductive drum. Conventionally, as an example of such image-forming apparatus, there is known an image-forming apparatus in which an eccentric cam is arranged between a plate-shaped spacer and the LED head to thereby finely adjust, with the eccentric cam, the spacing distance in the optical axis direction (hereinafter referred to as “optical axis-direction distance) between the photoconductive drum and the LED head.
In a case that, as in the above-mentioned exposure device, the frame supporting the photoconductive drum (photoconductive body) is to be positioned with respect to the LED head (exposure member) by using a structure having a concave-convex shape, etc., it is necessary to construct the casing of the LED head with high precision and with high rigidity. Therefore, it is hitherto necessary to produce the casing of the LED head with the aluminum die casting, etc. When the LED head is produced with such material and such producing method, then there is a problem such that the LED head becomes large-sized and the production cost becomes higher.
Moreover, even if a positioning portion with the concave-convex positioning structure is formed in the casing, it is not easy to fix (firmly fix) the light-emitting element to the casing and while maintaining a positional relationship between the light-emitting section of the light-emitting element and the positioning portion with high precision. Therefore, the positional relationship between the light-emitting section of the light-emitting element and the concave-convex positioning structure in the conventional apparatus has unsatisfactory or low precision, and there is a problem such that the positioning precision between the photoconductive body and the light-emitting section is low when the casing provided with the concave-convex positioning structure is simply assembled into other member or component.
Further, since the above-described LED head is used in the vicinity of or closely to the photoconductive drum, there is a fear that when the image-forming apparatus such as a printer is used for a long period of time, toner scattered from the photoconductive drum, etc. and/or paper powder generated from a paper sheet, etc. are attached or adhered to the lower surface of the lens array, which in turn lower the image quality. In this case, it is possible to remove the toner, etc. from the lower surface of the lens array by wiping the lower surface with a cloth or the like. However, when the corner portions on the both ends of the lens array are pointed or sharp, the cloth, etc. is caught or hooked by the corner portion(s), which in turn makes the cleaning operation with the cloth, etc. complicated. Moreover, when the cloth caught at the corner portion is torn and the fiber generated from the torn portion of the cloth is adhered to the lower surface of the lens array, there is a fear that the image quality is further lowered.
In addition, in the conventional technique (apparatus), the size of the eccentric cam and/or the spacer needs to be very small since the optical axis-direction distance is short, giving rise to the limitation to the precision in adjustment by the eccentric cam and the cam stroke. If such limitation is generated, it is not possible to set the optical axis-direction distance highly precisely, giving rise to a possibility that the image quality is lowered.
The inventors of the present application have developed a structure provided with a support frame which supports the LED head; a spacing distance-maintaining member (corresponding to the spacer) which maintains the spacing distance (distance) between the support frame and the photoconductive drum; and a cam which is arranged between the support frame and the LED head. With this structure, there is no need to provide any spacing distance-maintaining member or cam between the LED head and the photoconductive drum in the optical axis-distance which is short, thus solving the problems described above associated with the limitation to the precision in adjustment by the eccentric cam and the cam stroke and consequently the lowering of image quality.
However, with the above-described structure, when an excessive force is applied to the LED head upon, for example, cleaning the LED head, the LED warps with the cam as the warpage point and is elastically deformed in some cases. If the LED head is elastically deformed in such a manner, then the direction of the light emitted from the LED head is deviated from the normal direction, thus leading to a problem such that the image quality is lowered.